Because of wear and other effects, rotors, such as fans, turbines, shafts and motors, must be periodically re-balanced so that they can operate more efficiently. As a part of this balancing procedure, the rotor is analyzed to determine where it is out of balance, i.e.--heavy spots are located, and then counterbalancing weight is added to the rotor to restore its balance. As used herein "rotor" is used in a broad sense to mean rotating members.
The location of a heavy spot is determined in reference to an arbitrary mark that is placed on the rotor, and is expressed in units of degrees away from the reference mark. However, while it is easy to communicate a quantity in degrees, it has traditionally been confusing to express that quantity in reference to a rotating shaft.
For example, to express a location as 65.degree. clockwise, there is confusion as to whether rotor must be rotated 65.degree. in a clockwise direction, or the angle measured in a clockwise direction, in order to find the appropriate location. These two methods will locate different heavy spots, and one is wrong. Adding to the confusion is the fact that rotors have two ends, and clockwise rotation at the one end is counter clockwise rotation at the other.
For example, a hot spot may be expressed as "45 degrees against rotation", and there is a tendency to rotate the rotor against rotation, as opposed to measuring the angle against rotation. Typically an operation is performed to locate the heavy spot as an angle measured with regard to a reference mark on the shaft. The measured angle is given as "against rotation" and the operator may interpret this to mean that he should rotate the shaft from the reference mark in a direction against the rotation of the shaft. Of course, if the measured angle was intended to indicate a direction of measurement, as opposed to a direction of rotation, the shaft has been rotated in the wrong direction. Maintenance personnel have difficulty remembering that angles indicated to be against rotation require rotation of the shaft in a "with rotation" direction.
Additional confusion is encountered in referring to directions or locations as being left or right. The direction may be reversed depending on which end of the rotor is used as a reference and depending on whether left or right is referenced at the top or bottom of a horizontal rotor.
A technician who performs rotor balancing procedures daily may establish his own convention, but those who come after him, or work with him, are likely to employ different methods, and may have problems interpreting the information that to him was perfectly clear.
Those who infrequently perform balancing operations may have to spend great amounts of time resolving this problem each time they balance a rotor, not remembering how they had done it previously. Of particular concern is that balancing technicians may decide upon a different method of reference every time they perform a balancing operation, making it impossible to recreate and build upon the work which they have done. The ability to make accurate, consistent and repeatable angular measurements for balancing has become significantly more critical with advances in modern balancing instrumentation. The exact positions of dynamic sensors relative to a fixed reference is key to one-run trim balancing techniques and specialized calculations that are available in state-of-the-art technology.
This invention solves the problem of imprecise rotational direction indication, and provides both the journeyman and layman alike with a consistent and simple device for measuring, and a method for communicating and using, rotational position information.
Additional advantages of the invention will in part be set forth in the description which follows, and in part will appear from the description. The advantages of the invention may be realized and obtained by means of the embodiments particularly pointed out, and also by those embodiments within the spirit of the appended claims.